Area Forecast Discussion
Issued by NWS Shreveport, LA

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FXUS64 KSHV 151834

Area Forecast Discussion
National Weather Service Shreveport LA
134 PM CDT Tue Aug 15 2017

Scattered diurnal sea breeze convection shifting nwd into srn cwa
but mainly east of KLFK. Thus, all terminal location, besides
possibly KMLU later this aftn, will be removed from convection.
a few mvfr decks continuing into aftn. More mvfr will develop near
daybreak Tue but fog should not be an issue as southerly winds to
continue overnight, and increase to around 10 kts Tue, with a few
higher gusts, especially at KTYR and KGGG terminals./07/


.PREV DISCUSSION... /issued 1031 AM CDT Tue Aug 15 2017/

A weak surface boundary across southern Arkansas has allowed for
scattered showers across the I-30 corridor this morning.
Additionally, showers and thunderstorms have been surging north
from the Gulf of Mexico along a weakness on the western periphery
of a mid-level ridge. For this forecast update, went ahead and
increased rain chances across portions of north Louisiana,
southern Arkansas, southeast Oklahoma, and extreme northeast
Texas. Mid-level cloud cover should be sufficient to regulate
temperatures such that heat index values will remain at or below
105 degrees. /05/

PREV DISCUSSION... /issued 503 AM CDT Tue Aug 15 2017/

The morning GOES-R satellite imagery depicts an extensive AC shield
developing across much of the region this morning, between a pair of
shortwave troughs, one of which is helping to drive sct convection
over Nrn and Cntrl AR, and the second over the TX/OK Panhandles, and
the weak ridging aloft that has developed along the Nrn Gulf coast.
Meanwhile, the morning sfc analysis reveals our stationary front still
residing along the Red River of Srn OK/N TX extending E into far Srn
AR, which has shown signs of drifting N over the last few hours. The
short term progs are in good agreement with this sfc bndry lifting N
out of the forecast area by midday, with this bndry and the secondary
shortwave over the Panhandle region maintaining the sct convection N
of the area this afternoon over Ern OK/Ncntrl AR. The progs are also
suggesting that the AC shield will persist today, and thus limiting
the extent of max temps this afternoon, mainly in the lower to mid
90s, despite the very warm 09Z temps noted areawide attm. Despite the
wet grounds from the recent heavy rains, mixing will be limited today,
but believe that Heat Advisory criteria this afternoon will be
marginal over portions of E TX/Wrn LA given the extensive AC canopy
expected to linger. Meanwhile, the progs continue to suggest a
weakness aloft rounding the Wrn periphery of the upper ridge, which
should help trigger sct convection late this morning through the
afternoon over Srn and Ern LA, some of which may affect the SE zones
mainly this afternoon. Have maintained low to mid chance pops for
these areas, tapering pops to slight chance for the Lower Toledo Bend
Country across Ncntrl LA.

The Gulf Coast ridge will continue to build W into Cntrl and SE TX
Wednesday, although isolated to widely sct convection will remain
possible along the outer rim of the ridge over Deep E TX and the
Srn/Ern sections of Ncntrl LA. However, increasing subsidence and a
reduction in the AC cigs should result in hotter max temps over a
larger portion of the area, with limited mixing given PW`s of 1.8-2.0+
inches resulting in heat indices reaching Heat Advisory criteria over
a larger portion of the area. The progs depict the ridge amplifying
from TX along the Gulf coast Thursday, which should result in the
expanding heat over much of the region. A fly in the ointment though
is the broad upper troughing noted on the Great Basin this morning,
which will shift E into the Rockies late tonight and across the Plains
Wednesday. Sct convection should fire Wednesday afternoon ahead of the
trough along the Srn extention of this trough and near the attendant
sfc front over Cntrl and NE OK, with the convection possibly
congealing into a line along associated mesoscale bndrys and affect
portions of N TX, extreme SE OK, and adjacent Wrn AR before weakening
Thursday morning. Have continued mention of low to mid chance pops
late Wednesday night/Thursday morning across the far NW zones, which
may build a tad farther S into extreme NE TX/SW AR Thursday afternoon
atop the flattening ridge.

The ridging aloft remains progged to continue retrograding W Friday
becoming centered over TX, as weak shortwave energy in the NW flow
begins to drop SE ahead of an amplifying trough over the Plains and
upper Midwest. This should aid in the development of sct convection
over the Nrn and Ern half of the region, potentially enhanced during
peak heating/instability. Weaknesses aloft may linger this
weekend/early next week over the Nrn and Ern zones along the outer
periphery of the TX ridge thus focusing sct convection each day.
However, temps look to remain near climo through the weekend and the
end of the extended period.

Prelims to follow below...



SHV  94  78  95  78 /  20  10  10  10
MLU  92  75  93  76 /  30  10  20  10
DEQ  91  74  93  75 /  30  10  10  30
TXK  92  76  93  77 /  20  10  10  10
ELD  92  76  93  76 /  30  10  10  10
TYR  94  78  95  78 /  10  10  10  10
GGG  94  78  94  78 /  10  10  10  10
LFK  95  77  95  78 /  10  10  20  10



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